Orbital Tensioner

ABSTRACT

An orbital tensioner comprising an annular base, a ring journalled to the annular base on a ball bearing, said ring having a ring axis of rotation (A-A), a first pulley journalled to the ring, a first pulley axis of rotation (B-B) offset from the ring axis of rotation (A-A), a pivot arm pivotally mounted to the ring, a pivot arm pivot axis (C-C) offset from the ring axis of rotation (A-A), a second pulley journalled to the pivot arm, a torsion spring biasing the pivot arm in a first direction, the ball bearing having a first race and a second race, the ring fixed to the first race, the annular base fixed to the second race, and a damping mechanism frictionally disposed between the ring and the base.

FIELD OF THE INVENTION

The invention relates to an orbital tensioner, and more particularly, toan orbital tensioner having a ball bearing having a first race and asecond race, a ring mounted to the ball bearing first race, and anannular base mounted to the ball bearing second race.

BACKGROUND OF THE INVENTION

A multi-ribbed belt is commonly used on automotive vehicles to transmitpower between the engine crankshaft and accessory components. On aconventional drive, engine crankshaft pulley drives accessories via onebelt or multi belts. A tensioner is usually used when multi accessoriesare driven via a belt. Even when the tensioner arm is positionedproperly, belt installation tension can change slightly with respect tolength tolerance of the belt.

Motor-generator units (MGU) are used to implement BSG (beltstarter-generator) IC engine start-stop, torque assist to boost engineacceleration and recuperation to generate electricity in addition tonormal electrical generation by an alternator during IC engineoperation. Significant fuel savings and reduction of exhaust can beachieved by using BSG technology.

To control tension in two different driving modes, namely, MGU drivingand MGU generating with engine driving, an orbital style tensioner wasdeveloped. The tensioner typically has a rotary ring and a pivot armconnected by one spring to the rotary ring. The tensioner is mounted tothe MGU. This form of tensioner can control belt operating tension inboth modes: motoring and generating. However, unlike a conventionalsingle arm tensioner, it is not practical to position the orbitaltensioner pulleys in an optimized way to reduce tension variation.Installation tension changes, due to belt length tolerances and pulleyposition and size, can be significantly higher than for a single armtensioner. Belt tension is an important factor determining friction lossor power loss of a belt drive and so it is desirable to lower belttension without sacrificing system functional performance.

The prior art utilizes plastic bushings between the base and rotary ringto facilitate movement.

Representative of the art is US20190078667 which discloses a tensionercomprising a base defining a hole, the hole having a center C, the holehaving a diameter sufficient to receive a driven pulley, a rotary armengaged with the base by a retaining member connected to the base, therotary arm rotatable about the center C, a pivot arm mounted to therotary arm on a pivot, the pivot offset from center C, a first pulleyjournalled to the rotary arm, a second pulley journalled to the pivotarm, a torsion spring engaged between the rotary arm and the pivot armfor biasing the second pulley toward the first pulley, a damping memberfrictionally engaged between the base and the rotary arm, and the rotaryarm defining a portion for receiving a first pulley fastener whereby afirst pulley position is adjustable.

What is needed is an orbital tensioner having a ball bearing having afirst race and a second race, a ring mounted to the ball bearing firstrace, and an annular base mounted to the ball bearing second race. Thepresent invention meets this need.

SUMMARY OF THE INVENTION

The primary aspect of the invention is to provide an orbital tensionerhaving a ball bearing having a first race and a second race, a ringmounted to the ball bearing first race, and an annular base mounted tothe ball bearing second race.

Other aspects of the invention will be pointed out or made obvious bythe following description of the invention and the accompanyingdrawings.

The invention is an orbital tensioner comprising an annular base, a ringjournalled to the annular base on a ball bearing, said ring having aring axis of rotation (A-A), a first pulley journalled to the ring, afirst pulley axis of rotation (B-B) offset from the ring axis ofrotation (A-A), a pivot arm pivotally mounted to the ring, a pivot armpivot axis (C-C) offset from the ring axis of rotation (A-A), a secondpulley journalled to the pivot arm, a torsion spring biasing the pivotarm in a first direction, the ball bearing having a first race and asecond race, the ring fixed to the first race, the annular base fixed tothe second race, and a damping mechanism frictionally disposed betweenthe ring and the base.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims. The novel features which are believed to be characteristic ofthe invention, both as to its organization and method of operation,together with further objects and advantages will be better understoodfrom the following description when considered in connection with theaccompanying figures. It is to be expressly understood, however, thateach of the figures is provided for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specification, illustrate preferred embodiments of the presentinvention, and together with a description, serve to explain theprinciples of the invention.

FIG. 1 is a back perspective view of the tensioner.

FIG. 2 is a front perspective view of the tensioner.

FIG. 3 is a front plan view of the tensioner.

FIG. 4 is an exploded view.

FIG. 5 is a cross section 5-5 in FIG. 3.

FIG. 6 is an MGU system with the inventive tensioner.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a back perspective view of the tensioner. Tensioner 1000comprises a base 10, ring 20 and pivot arm 30. Ball bearing 40 isdisposed between base 10 and ring 20. Base 10 and ring 20 are journalledtogether on bell bearing 40.

Pulley 21 is journalled to ring 20 on bearing 22. Pulley 31 isjournalled to pivot arm 30 on bearing 34. The axis of rotation B-B ofpulley 21 is offset from the axis of rotation A-A of bearing 40, andthereby of ring 20.

Pivot arm 30 pivots about pivot axis C-C. Ring 20 rotationallytranslates with respect to base 10 about axis A-A. In operation ring 20oscillates between different positions about axis A-A depending on belttension variations and the MGU system operating conditions.

The belt is trained in an accessory drive system. The belt engagespulley 21 and pulley 31. The accessory drive system may comprise certainengine driven accessories including water pump, fuel injection pump, airconditioning compressor, oil pump, power steering pump to name a few,see FIG. 6.

Base 10 has an annular or torus-like form and comprises mounting bracketwith holes 11. Mounting bracket is used to attach the tensioner to amotor generator unit (MGU) using fasteners such as bolts. Axis A-Aaligns with an axis of rotation of an MGU shaft MGUS, see FIG. 6. Thebase annular form aligns with axis A-A.

In the disclosed embodiment bearing 40 comprises a 30BD40 double rowangular contact bearing available from Bauhaun, Taide, NSK, Nachi or SKFfor example. Others offer suitable double row bearings as well. Anexample size for the embodiment described herein is 30 mm ID×55 mm OD×23mm wide. A sealed deep groove single row bearing may also be usedaccording to the needs of a user. An example size single row bearing is30 mm ID×55 mm OD×13 mm wide. Either style of bearing is preferablysealed to retain a lubricant and resist contamination. The lubricant cancomprise either grease or oil known in the art.

Bearing 40 is press fit into base 10 and ring 20. Bearing 40 inner race41 is staked to ring 20. Bearing 40 outer race 42 is staked tocylindrical portion 12 of base 10. Staking is generally known as meansto fix two components together, for example, see among others:https://www.assemblymag.com/articles/87755-assembly-presses-crimping-staking-swaging-clinching.

Use of ball bearing 40 improves long term operational alignment of ring20 with base 10. Pulleys 21, 31 are displaced outward from the plane ofbase 10, so when a belt tensile load is applied a couple is produced.The couple acts to rotate ring 20 with respect to base 10. Prior artorbital tensioners utilize plastic bushings to resist the couple andmaintain coplanar alignment of the base and ring. However, plasticbushings deteriorate with time leading to gradual misalignment of thering and base and thereby misalignment of the pulleys with the beltplane. This in turn causes undesirable noise and premature wear of thebelt. The belt can ultimately disengage from the pulleys if themisalignment is allowed to continue unabated. Undue noise can become afactor as well. On the other hand, the ball bearing is more durable andlasts longer and holds alignment between the ring and base moreaccurately over time compared to plastic bushings. A double row bearingis preferable to a single row bearing since it is more resistant to“rock” compared to a single row bearing. However, depending on thesystem design either may be selected. Needle bearings may be used aswell with equal success.

FIG. 2 is a front perspective view of the tensioner. Bearing 40 innerrace 41 is press fit onto cylindrical portion 25 of ring 20. Race 41 isstaked to portion 25. Portion 25 may comprise a hollow cylinder or solidshaft. Pin 37 engages a hole 38 in ring 20 during installation. Pin 37holds pivot arm 30 in a predetermined position.

FIG. 3 is a front plan view of the tensioner. In this embodiment pulleys21, 31 are on the same side of the tensioner, typically facing an MGU.This can be referred to as an inverted design.

FIG. 4 is an exploded view. The damping mechanism comprises elements 51,52, 53. Friction element 53 engages ring 20. Wave spring 51 presses onsteel ring 52. Ring 52 protects element 53 by distributing the normalforce from wave spring 51 to friction element 53. Friction element 53 islocked to base 10 by tabs 54 so as to prevent a relative rotation ofelement 53. Friction element 53 damps movement of ring 20.

Pulley 21 is journalled on bearing 22. Dust shield 24 prevents debrisfrom entering bearing 22. Bolt 23 retains the dust shield 24 and bearing22, and thereby pulley 21 on ring 20.

Pulley 31 is journalled on bearing 34. Dust shield 35 keeps debris fromentering bearing 34. Bolt 36 retains the dust shield 35 and bearing 34,and thereby pulley 31 on pivot arm 30.

Pin 37 temporarily engages between pivot arm 30 and base 10. Removablepin 37 locks pivot arm 30 in a predetermined installation position. Pin37 is removed by an installer after the tensioner is installed in itsfinal position on an MGU, thereby releasing the pivot arm 30 and pulley31 to apply a load to a belt.

End 39 of spring 32 bears upon stop 26. Spring 32 is loaded in anunwinding direction. End 391 bears upon a stop 392 in pivot arm 30.

FIG. 5 is a cross section 5-5 in FIG. 3. Double row bearing 40 is shown.Inner race 41 is press fit onto cylindrical portion 25. Outer race 42 ispress fit into cylindrical portion 12. Use of a bearing negates the needfor a prior art connection wherein the ring clamps the base or the baseclamps the ring. Instead, the inventive tensioner links the ring andbase entirely though the bearing without need of a clamp or overlapstyle joint.

Bearing 40 provides more accurate movement of the ring on the base withless movement resistance when compared to a plastic bushing.

Damping mechanism 51, 52, 53 is engaged between the base 10 and ring 20to damp ring movement. Tabs 54 engage respectively portions 13 in base10 to prevent movement of friction element 53 relative to base 10. Inthis way the frictionally damped movement is between friction element 53and ring 20. In an alternate embodiment friction element 53 is locked toring 20 with relative frictional movement occurring between frictionelement 53 and base 10 with equal effect.

FIG. 6 is an MGU system with the inventive tensioner. Tensioner 1000 ismounted to an MGU which is part of an accessory drive system. Belt B istrained between the pulley on an engine crankshaft CRK, air conditionercompressor AC and the MGU with an MGU shaft MGUS. An idler pulley IDLprovides for proper routing of the belt on the engine. Pivot arm 30presses pulley 31 against the belt in order to impart a belt tensileload. The belt load prevents the belt from slipping on the systempulleys, which can cause noise and premature wear of the belt.

For stop/start operation, the MGU generates electrical power when theengine is operating. The MGU is driven by the engine in this mode. Whenthe engine is stopped the MGU becomes the driver and provides startingpower for the engine. The MGU keeps the air conditioning compressoroperating by use of an electric clutch (not shown). The electric clutchis mounted to the air conditioning compressor and is controlled by avehicle ECU. The crankshaft CRK may also comprise a one-way clutch (notshown) to facilitate operation.

An orbital tensioner comprising an annular base, a ring rotationallyengaged with the annular base with a ball bearing, the ring having aring axis of rotation A-A, a first pulley journalled to the ring andhaving a first pulley axis of rotation B-B that is offset from the ringaxis of rotation A-A, a pivot arm pivotally mounted to the ring, thepivot arm pivot axis C-C is offset from the ring axis of rotation A-A, asecond pulley journalled to the pivot arm, a torsion spring biasing thepivot arm in a first direction, the ball bearing having a first race anda second race, the ring staked to the first race, the annular basestaked to the second race, and a damping mechanism frictionally disposedbetween the ring and the base.

An orbital tensioner comprising an annular base, a ring journalled tothe annular base on a ball bearing, said ring having a ring axis ofrotation A-A, a first pulley journalled to the ring, a first pulley axisof rotation B-B offset from the ring axis of rotation A-A, a pivot armpivotally mounted to the ring, a pivot arm pivot axis C-C offset fromthe ring axis of rotation A-A, a second pulley journalled to the pivotarm, a torsion spring biasing the pivot arm in a first direction, theball bearing having a first race and a second race, the ring fixed tothe first race, the annular base fixed to the second race, and a dampingmechanism frictionally disposed between the ring and the base.

An orbital tensioner comprising a base, a ring and the base journalledtogether on a ball bearing, said ring having a ring axis of rotationA-A, a first pulley journalled to the ring, a first pulley axis ofrotation B-B offset from the ring axis of rotation A-A, a pivot armpivotally mounted to the ring, a pivot arm pivot axis C-C is offset fromthe ring axis of rotation A-A, a second pulley journalled to the pivotarm, a torsion spring biasing the pivot arm in a first direction, and adamping mechanism frictionally disposed between the ring and the base.

Although a form of the invention has been described herein, it will beobvious to those skilled in the art that variations may be made in theconstruction and relation of parts without departing from the spirit andscope of the invention described herein. Unless otherwise specificallynoted, components depicted in the drawings are not drawn to scale.Numeric information is by example and is not intended to limit the scopeof the invention unless indicated otherwise. Further, it is not intendedthat any of the appended claims or claim elements invoke 35 U.S.C. § 112(f) unless the words “means for” or “step for” are explicitly used inthe particular claim. The present disclosure should in no way be limitedto the exemplary embodiment or numerical dimensions if any illustratedin the drawings and described herein.

We claim:
 1. An orbital tensioner comprising: an annular base; a ringjournalled to the annular base on a ball bearing, said ring having aring axis of rotation (A-A); a first pulley journalled to the ring, afirst pulley axis of rotation (B-B) offset from the ring axis ofrotation (A-A); a pivot arm pivotally mounted to the ring, a pivot armpivot axis (C-C) offset from the ring axis of rotation (A-A), a secondpulley journalled to the pivot arm; a torsion spring biasing the pivotarm in a first direction; the ball bearing having a first race and asecond race; the ring fixed to the first race; the annular base fixed tothe second race; and a damping mechanism frictionally disposed betweenthe ring and the base.
 2. The orbital tensioner as in claim 1, whereinthe ball bearing is staked to the ring.
 3. The orbital tensioner as inclaim 1, wherein the ball bearing is staked to the base.
 4. The orbitaltensioner as in claim 1, wherein the damping mechanism comprises afriction member and a spring.
 5. The orbital tensioner as in claim 1,wherein the ball bearing comprises a double row bearing.
 6. The orbitaltensioner as in claim 1, wherein the ball bearing is a sealed bearing.7. The orbital tensioner as in claim 4, wherein the spring comprises awave spring.
 8. The orbital tensioner as in claim 1, wherein the ballbearing first race is an inner race.
 9. The orbital tensioner as inclaim 1, wherein the ball bearing first race is an outer race.
 10. Anorbital tensioner comprising: an annular base; a ring rotationallyengaged with the annular base with a ball bearing, the ring having aring axis of rotation (A-A); a first pulley journalled to the ring andhaving a first pulley axis of rotation (B-B) that is offset from thering axis of rotation (A-A); a pivot arm pivotally mounted to the ring,the pivot arm pivot axis (C-C) offset from the ring axis of rotation(A-A), a second pulley journalled to the pivot arm; a torsion springbiasing the pivot arm in a first direction; the ball bearing having afirst race and a second race; the ring staked to the first race; theannular base staked to the second race; and a damping mechanismfrictionally disposed between the ring and the base.
 11. The orbitaltensioner as in claim 10, wherein the ball bearing is a double rowbearing.
 12. The orbital tensioner as in claim 10, wherein the ballbearing is a single row bearing.
 13. The orbital tensioner as in claim12, wherein the single row bearing is a deep groove single row bearing.14. The orbital tensioner as in claim 11, wherein the damping mechanismcomprises a wave spring and friction element.
 15. An orbital tensionercomprising: a base; a ring, the ring and base journalled together on aball bearing, said ring having a ring axis of rotation (A-A); a firstpulley journalled to the ring, a first pulley axis of rotation (B-B)offset from the ring axis of rotation (A-A); a pivot arm pivotallymounted to the ring, a pivot arm pivot axis (C-C) is offset from thering axis of rotation (A-A), a second pulley journalled to the pivotarm; a torsion spring biasing the pivot arm in a first direction; and adamping mechanism frictionally disposed between the ring and the base.16. The orbital tensioner as in claim 15, wherein the ball bearingcomprises a sealed double row bearing.
 17. The orbital tensioner as inclaim 15, wherein the ball bearing comprises a sealed deep groove singlerow bearing.
 18. The orbital tensioner as in claim 15, wherein thedamping mechanism comprises a wave spring and a friction element. 19.The orbital tensioner as in claim 15, wherein the base and the ring arestaked to the ball bearing.
 20. The orbital tensioner as in claim 15further comprising a removable pin engaged with the pivot arm and thebase.